1. Field of Invention
The present invention relates generally to water disinfection systems, and more specifically, but not by way of limitation, to water disinfection reactors.
2. Description of Related Art
Examples of disinfection reactors are disclosed in U.S. Pat. No. 3,235,003 and in Pub. No. US 2013/0292342.
Water related to human activity has to be of proper quality to avoid waterborne diseases. The disinfection of water for consumption has proven to be effective for destroying or deactivating pathogenic microorganisms (Cardot, 2002), especially those responsible for typhoid fever and cholera. Pathogenic microorganisms include bacteria, fungi, protozoa, and insects (Moles, 2007). Bacteria have a relatively weak resistance to disinfection, while protozoa and viruses have a relatively high resistance to disinfection.
Chlorination has become a common method for disinfecting water and is generally effective at reacting with and destroying or deactivating most microorganisms. Since the discovery and use of chlorine as a disinfectant, the number of illnesses and deaths related to the consumption of contaminated water has significantly decreased. Additionally, apart from destruction or deactivation of microorganisms, chlorine can be used to eliminate metals and undesirable tastes or smells in water. Chlorination is a simple process and is relatively inexpensive.
However, chlorine also reacts with organic material in the water (e.g. decaying leaves). These chemical reactions produce a family of harmful disinfection by-products (DBP), most commonly trihalomethanes (THM). DBP concentration in water depends on many factors; such as, for example, the amount organic matter, bromide ions, and free chlorine in the water, as well as the pH and temperature of the water. Even further, the amount of time that the chlorine is in contact with the water (exposure time) plays a large role in the amount of harmful DBP produced by chlorination. The majority of these harmful DBPs cannot be eliminated by further treatment. Therefore, exposure time needs to be carefully controlled—too short of an exposure time may result in inadequate disinfection, while too long of an exposure time may result in harmful DBP production.
Current disinfection reactors and processes are unable to sufficiently control the exposure time between water and a disinfectant. For example, when water and a disinfectant are introduced into existing reactors, large recirculation regions tend to develop. Water flow in the recirculation regions may travel slowly through the reactor, undergoing a relatively long exposure time to the disinfectant. On the other hand, water flow that avoids the recirculation regions may travel quickly through the reactor, undergoing a relatively short exposure time to the disinfectant. In at least this way, current disinfection reactors and processes exhibit a risk for both inadequate disinfection and harmful DBP production.